- CYCLIC PEROXIDE OXIDATION OF AROMATIC COMPOUND PRODUCTION AND USE THEREOF
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The present invention provides a method for converting an aromatic hydrocarbon to a phenol by providing an aromatic hydrocarbon comprising one or more aromatic C-H bonds and one or more activated C-H bonds in a solvent; adding a phthaloyl peroxide to the solvent; converting the phthaloyl peroxide to a di-radical; contacting the di-radical with the one or more aromatic C-H bonds; oxidizing selectively one of the one or more aromatic C-H bonds in preference to the one or more activated C-H bonds; adding a hydroxyl group to the one of the one or more aromatic C-H bonds to form one or more phenols; and purifying the one or more phenols.
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Page/Page column 9; 10
(2014/10/15)
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- Metal-free oxidation of aromatic carbon-hydrogen bonds through a reverse-rebound mechanism
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Methods for carbon-hydrogen (C-H) bond oxidation have a fundamental role in synthetic organic chemistry, providing functionality that is required in the final target molecule or facilitating subsequent chemical transformations. Several approaches to oxidizing aliphatic C-H bonds have been described, drastically simplifying the synthesis of complex molecules. However, the selective oxidation of aromatic C-H bonds under mild conditions, especially in the context of substituted arenes with diverse functional groups, remains a challenge. The direct hydroxylation of arenes was initially achieved through the use of strong Bronsted or Lewis acids to mediate electrophilic aromatic substitution reactions with super-stoichiometric equivalents of oxidants, significantly limiting the scope of the reaction. Because the products of these reactions are more reactive than the starting materials, over-oxidation is frequently a competitive process. Transition-metal-catalysed C-H oxidation of arenes with or without directing groups has been developed, improving on the acid-mediated process; however, precious metals are required. Here we demonstrate that phthaloyl peroxide functions as a selective oxidant for the transformation of arenes to phenols under mild conditions. Although the reaction proceeds through a radical mechanism, aromatic C-H bonds are selectively oxidized in preference to activated-H bonds. Notably, a wide array of functional groups are compatible with this reaction, and this method is therefore well suited for late-stage transformations of advanced synthetic intermediates. Quantum mechanical calculations indicate that this transformation proceeds through a novel addition-abstraction mechanism, a kind of 'reverse-rebound' mechanism as distinct from the common oxygen-rebound mechanism observed for metal-oxo oxidants. These calculations also identify the origins of the experimentally observed aryl selectivity.
- Yuan, Changxia,Liang, Yong,Hernandez, Taylor,Berriochoa, Adrian,Houk, Kendall N.,Siegel, Dionicio
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p. 192 - 196
(2013/08/23)
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- Process for separating tocopherol homologues
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Methods for separating gamma and delta homologues of tocopherol are described.
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Page/Page column 2-3
(2008/06/13)
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- Biotenside esters and phosphatides with vitamin-D and vitamin-E compounds
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New biotenside esters and phosphatides formed with Vitamin-D and Vitamin-E compounds possessing a pronounced antitumor activity, processes for their production as well as for the preparation of concentrates and pharmaceutical compositions containing these new esters and phosphatides, and their use for treating tumors are described.
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- The substrate specificity of tocopherol cyclase
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The substrate specificity of the enzyme tocopherol cyclase from the blue-green algae Anabaena variabilis (Cyanobacteria) was investigated with 11 substrate analogues revealing the significance of three major recognition sites: (i) the OH group at C(1) of the hydroquinone, (ii) the (E) configuration of the double bond, and (iii) the length of the lipophilic side chain. Experiments with two affinity matrices suggest that substrates approach the enzyme's active site with the hydrophobic tail.
- Stocker, Achim,Fretz, Heinz,Frick, Haroun,Ruettimann, August,Woggon, Wolf-Dietrich
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p. 1129 - 1134
(2007/10/03)
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- Electron-transfer reactions of alkyl peroxy radicals
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One-electron-transfer reactions of alkyl peroxy radicals were studied by pulse radiolysis of aqueous solutions. At pH 13, the methyl peroxy radical was found to rapidly, k = 1 × 105-4.9 × 107 s-1, and quantitatively oxidize various organic substrates with E13 = 0.13-0.76 V vs NHE. On the other hand, this radical was unreactive with compounds with E13 ≥ 0.85 V. Consequently, E13 of the methyl peroxy radical is higher than 0.76 V and lower than 0.85 V, which means that E7 is in the range 1.02-1.11 V. At pH 8, the rate constants of the oxidation of four ferrocene derivatives by the alkyl peroxy radicals ranged from 7.1 × 104 M-1 s-1 for ferrocenedicarboxylate (E8 = 0.66 V) to 2.3 × 106 M-1 s-1 for (hydroxymethyl)ferrocene (E8 = 0.42 V). These rate constants were used to evaluate the reduction potential and self-exchange rate of alkyl peroxy radicals in neutral media from the Marcus equation. The calculated E7 = 1.05 V is in excellent agreement with the estimated E7 = 1.02-1.11 V and with one of the perviously published values E7 = 1.0 V, but the value is in excellent agreement higher than the other E7 ~ 0.6 V. It is suggested that the high reorganization energy, λ = 72 kcal mol-1 redox couple originates from the requirement for solvent reorganization due to the solvation of hydroperoxide anion in the transition state. In support of this are the activation parameters of the reaction of the methyl peroxy radical with uric acid. The activation entropy is 9 eu lower at pH 7.3 than it is at pH 13.2, whereas the activation enthalpies are unchanged. The importance of entropy control was verified in the reactions of cyclohexyl peroxy radicals with α- and δ-tocopherol in aerated cyclohexane (ΔH+ ≈ 0 kcal/mol, and ΔS+ = -25 and -26 eu). The implications of these findings on the inactivation of alkyl peroxy radicals in general are discussed.
- Jovanovic, Slobodan V.,Jankovic, Ivana,Josimovic, Ljubica
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p. 9018 - 9021
(2007/10/02)
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- Reaction of 8a-Hydroperoxy Tocopherones with Ascorbic Acid
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8a-Hydroperoxy tocopherones, prepared from the photooxidation of α-, γ- and δ-tocopherols, were allowed to react with ascorbic acid in ethanol.The hydroperoxy tocopherones were reduced to 8a-hydroxy and 8a-ethoxy tocopherones which in turn were reduced to tocopherols by ascorbic acid.The tendency of the hydroperoxy tocopherones to form tocopherols during the reaction correlated with vitamin E activities of tocopherols.The results is indicate that α-tocopherol and ascorbic acid can act synergistically on the quenching of 1O2.The inhibitory effects of α-tocopherol and ascorbic acid were examined on the chlorophyll-sensitized photooxidation of methyl linoleate and soybean oil.At initial stage of the oxidation, the inhibitory effect of α-tocopherol was lengthened in the presence of ascorbic acid.
- Yamauchi, Ryo,Kato, Koji,Ueno, Yoshimitsu
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p. 2855 - 2862
(2007/10/02)
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- 2-METHYL-6-PHYTYLQUINOL AND 2,3-DIMETHYL-5-PHYTYLQUINOL AS PRECURSORS OF TOCOPHEROL SYNTHESIS IN SPINACH CHLOROPLASTS
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The incorporation of from SAM- into precursors indicates the following sequence of tocopherol synthesis in spinach: 2-methyl-6-phytylquinol (6-phytyltoluquinol) (1a) -> 2,3-dimethyl-5-phytylquinol (phytylplastoquinol) (2a) -> γ-tocopherol (5a) -> α-tocopherol (6). 1a is a particularly preferred to 2-methyl-5-phytylquinol (1b) and 2-methyl-3-phytylquinol (1c). 1a only forms 2a. 2a is converted to 6 via 5a and, to a lesser extent, 2,5-dimethyl-6-phytylquinol (2b) to 6 via β-tocopherol (5b).Trimethylphytylquinol (3) is not an intermediate in the formation of 6.All reactions are independent of light. - Key Word Index - Spinacia oleracea; Chenopodiaceae; tocopherol biosynthesis; 2-methyl-6-phytylquinol; 2,3-dimethyl-phytylquinol; phytylquinol synthesis.
- Soll, Juergen,Shultz, Gernot
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p. 215 - 218
(2007/10/02)
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